General solid-state imaging devices use a buried photodiode structure as a light reception unit. Meanwhile, a solid-state imaging device having a structure which does not use a buried photodiode (stack-type solid-state imaging device) is also known (for example, refer to Patent Literature 1).
Patent Literature 1, for example, discloses a stack-type solid-state imaging device in which a photoelectric conversion layer is formed on a control electrode comprising a solid-state amplifying device and a transparent electrode layer is provided on the formed photoelectric conversion layer. The stack-type solid-state imaging device can convert, into an electrical signal, optical information at a good S/N ratio by exercising, to the control electrode, the operation of voltage applied to the transparent electrode layer via the photoelectric conversion layer.
In this way, the stack-type solid-state imaging device has a configuration in which a photoelectric conversion film is formed, via an insulating film, above a semiconductor substrate on which a pixel circuit is formed. Therefore, it is possible for a material having a large light absorption coefficient, such as amorphous silicon and the like, to be used in a photoelectric conversion film. For example, the amorphous silicon can mostly absorb green light having a wavelength of 550 nm at a thickness of about 0.4 nm.
Moreover, since the stack-type solid-state imaging device has a configuration without using a buried photodiode, the stack-type solid-state imaging device can increase capacity of a photoelectric conversion unit and magnify saturated charge. Furthermore, the stack-type solid-state imaging device can actively add capacity since charge is not completely transferred, and can realize a sufficient capacity even in a miniaturized pixel. Moreover, it is possible to form with a structure such as stack cell in a dynamic random access memory.